animation-ball physics

In this session were asked to animate 4 different types of animation of ball physics, the first being a short animation of a cartoon ball bouncing which required to draw to draw stretched circles throughout which from my prospective was fairly hard as my circles are not brilliant compared to drawing a normal circle.  

then for the second animation we were required to animate to real psychics of a bowling ball(black)/ a ping pong ball(yellow) and a tennis ball(purple). with this animation real physics were required and it took a quite a few attempts to make some form of realistic animation that was expected.